Thickened fuel compositions and method and material for thickening same

ABSTRACT

ALIPHATIC FUEL COMPOSITION SUCH AS GASOLINE, JET (TURBINE) FUEL, DIESEL FUEL AND THE LIKE ARE THICKENED TO DECREASE FLAMMABILITY HAZARDS EMPLOYING SOLUBLE POLYMERS CONTAINING MINOR AMOUNTS OF POLAR MATERIALS SUCH AS ACRYLIC ACID. SUCH FUEL DOES NOT INDUCE SULFIDATION ON COMBUSTION.

United States Patent ABSTRACT OF THE DISCLOSURE Aliphatic fuelcompositions such as gasoline, jet (turbine) fuel, diesel fuel and thelike are thickened to decrease flammability hazards employing solublepolymers containing minor amounts of polar materials such as acrylicacid. Such fuel does not induce sulfidation on combustion.

This application is a continuation-in-part of our copending applicationSer. No. 792,848, filed Jan. 21, 1969.

This invention relates to thickened aliphatic hydrocarbons, and moreparticularly relates to liquid aliphatic hydrocarbons thickened with aminor proportion of a polymeric additive.

It is desirable for many purposes to thicken liquid aliphatichydrocarbons. One particularly advantageous application of suchthickened hydrocarbons is in fuel for combustion engines such asaircraft engines, automobile engines and the like. The use of athickened fuel markedly reduces the fire hazard when a fuel tank isruptured by impact such as in the event of a crash or damage sustainedfrom gun fire. The requirements of such a thickened fuel are somewhatcontradictory in that an ideal crash-safe fuel would be a solid coherentmaterial which did not fragment or spread on impact. However,

in order for the fuel to be fed to an engine, it is necessary that it bepumped and drained from a fuel tank under the influence of gravity.Thus, a suitable fuel should have a viscous or gelatinous nature whennot subject to shear and behave essentially as a liquid when subjectedto shear such as shear imposed by a fuel pump. Beneficially, thethickened fuel under the influence of gravity should flow in the mannerof a liquid at a rate sufficient to permit the material to be Withdrawnfrom a fuel tank at a rate at least equal to the rate of fuelconsumption. It is highly desirable that minimal quantities of suchthickening agents be employed and that all components of the fuelmixture be volatile under combustion conditions and that the system besubstantially free from metal ions which induce sulfidation in internalcombustion engines. Such fuels are generally hydrocarbon compositions,and beneficially aliphatic hydrocarbon compositions. Hereinafter, theterm aliphatic hydrocarbon(s) shall include aliphatic hydrocarbons,cycloaliphatic hydrocarbons and mixtures thereof.

Aliphatic hydrocarbons operable in the invention include compounds thatmay be either branched or linear such as propane, butane, pentane,hexane, heptane, octane, nonane, decane, dodecane, propene, butene,1,3-butadiene, isoprene and the like saturated and unsaturated aliphatichydrocarbons. Exemplary of the cycloaliphatic hydrocarbons that can begelled or thickened in accordance with the present invention arecyclopentane, 1,1-dimethyl cyclopentane, 1,3 dimethyl cyclopentane,cyclohexane, methyl cyclohexane, ethyl cyclohexane, 2,4-dimethylcyclohexane and the like cycloaliphatic hydrocarbons.

Materials which may be gelled by practice of the present invention arethose which have solubility parameters "ice varying from about 6.8 to11. Solubility parameters are described by Hildebrand and Scott in TheSolubility of Nonelectrolytes, Reinhold, 1949, and by H. Burrel inSolubility Parameters, Interchemical Review, vol. 14, pages 3 and 31,1955. Solubility parameters of various hydrocarbons are hereinafter setforth:

Hydrocarbon: Parameters Low odor mineral spirits 6.9 Apco 140 7.3 TS-28solvent 7.4

.Apco 18 7.5 VM&P naphtha 7.6 Socal solvent 3 7.7 Apcothinner 7.8 Socalsolvent 2 7.9 Socal solvent 1 8.1 Turpentine 8.1 Terpene B 8.4 Solvesso1S0 8.5 Dipentene 8.5 Solvesso 8.6 Pine oil 8.6 Carbon tetrachloride 8.6Hi-fiash naphtha -a 8.7 Xylene 8.8 Toluene 8.9

Benzene 9.2 Monochlorobenzene 9.5 Tetralin 9.5 Isobutylene 6.7 Pentane7.0

Hexane 7.3

Heptane 7.4 Octane 7.6

Kerosene 8.2 Ethylbenzene 8.8 Methylcyclohexane 7.8 Cyclohexane 8.2

Other hydrocarbons which may be employed are mixtures comprisingessentially one or more materials of the foregoing classes ofhydrocarbons such as may be obtained by the distillation or alkylationof petroleum stocks, Examples of such are petroleum ether, gasoline,kerosene, benzine, ligroin, motor oil and the like.

Also useful in the practice of the present invention are the aromatichydrocarbons such as benzene, toluene, xylene and the like, either aloneor in admixture with each other, or aliphatic hydrocarbons. Ofparticular interest are such petroleum distillates as are commerciallyavailable for fuels such as those sold under the trade designation Jet-Aand Jet-B, both with and without deicing additives, and like turbinefuels. The hydrocarbon materials to be thickened should not bedehydrated, but should contain the customary traces of water present incommercial grade material.

Such hydrocarbon materials in accordance with the present invention arethickened by uniformly incorporating within the hydrocarbon body fromabout 0.2 to about 10 percent of a synthetic organic polymer soluble inthe hydrocarbon, advantageously the polymer having present in at least0.2 percent to 3 percent thereof an oxygen-containing polar compoundselected from the group consisting of olefincially unsaturatedcopolymerizable (a) acids containing up to 6 carbon atoms, such asacrylic acid, methacrylic acid, itaconic acid, citraconic acid; (b)amides containing up to 4 carbon atoms, such as acrylamide, and mixturesthereof; (c) hydroxy acrylic esters such as 2-hydroxyethyl methacrylate,2- hydroxypropyl methacrylate, B-hydroxypropyl methacrylate,Z-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 3-hydroxypropylacrylate; (d) sulphonic acids such as 2-sulphoethyl methacrylate,2-sulphoethyl acrylate, 3- vinylbenzenesulphonic acid,2-benzenesulphonic acid and the like.

Oil soluble polymers useful in the present invention includealkylstyrene polymers which are readily obtained by polymerization ofalkylstyrene monomers, with the oxygen-containing polar compound, thealkylstyrenes have alkyl groups containing from 3 to 20, and preferablyfrom 4 to 12, carbon atoms, and mixtures of styrene monomers containingan average of at least 3, and no more than 20, preferably from 4 to 12,aliphatic carbon atoms per aromatic ring. Effective thickening alkylstyrene polymers include: polymers of tertiary-alkylstyrenes such asp-tertiary-butylstyrene, p-tertiary-amylstyrene,p-tertiary-hexylstyrene, p-tertiary-octylstyrene,p-tertiary-dodecylstyrene, p-tertiary-octadecylstyrene andptertiary-eicosylstyrene; polymers of n-alkylsytrenes such asn-butylstyrene, n-amylstyrene, n-hexylstyrene, n-octylstyrene,n-dodecylstyrene, n-octadecylstyrene and n-eicosylstyrene; polymers ofsec-alkylstyrenes such as sec-butylstyrene, sec-hexylstyrene,sec-octylsytrene, sec-dodecylstyrene, sec-octadecylstyrene andsec-eiscosylstyrene; polymers of isoalkylstyrenes such asisopropylstyrene, isobutylstyrene, isohexylstyrene, isooctylstyrene,isododecylstyrene, isooctadecylstyrene and isoeiscosylstyrene andcopolymers thereof, as well as copolymers of such alkylstyrenes withstyrene and vinyl toluene, for example, such as a copolymer ofp-tertiary-butylstyrene and styrene in at least a 75 :25 mole ratiocontaining polymerized therein 1 percent acrylic acid; a copolymer ofn-amylstyrene and styrene in at least a 60:40 mole ratio containingpolymerized therein 1 percent itaconic acid; a copolymer ofn-hexylstyrene and styrene in at least a 50:50 mole ratio containingpolymerized therein 1 percent citraconic acid; a copolymer ofsec-dodecylstyrene and styrene in at least a 25:75 mole ratio containingpolymerized therein 1 percent acryl-amide; a copolymer ofisoeicosylstyrene and styrene in at least a 15:85 mole ratio and 1percent itaconic acid; a copolymer of p-tertiarybutylstyrene and vinyltoluene in at least a 67:33 mole ratio and 1 percent acrylic acid; acopolymer of secamylstyrene and vinyl toluene in at least a 50:50 moleratio and 2 percent methacrylic acid; a copolymer of noctylstyrene andvinyl toluene in at least a 29:71 mole ratio and 3 percent methacrylicacid; a copolymer of ndodecylstyrene and vinyl toluene in at least a19:81 mole ratio and 0.5 percent acrylic acid, and a copolymer ofsec-octadecylstyrene and vinyl toluene in at least a 12:88 mole ratioand 1.5 percent citraconic acid, alkyl acrylates such as laurylacrylate, di-Z-ethylhexyl acrylate, stearyl acrylate either ashomopolymers or copolymerized with an alkylstyrene. When employingalkylstyrenes, it is particularly beneficial to have included therein upto about 500 parts of isopropenylvinylbenzene per million parts of thealkylstyrene, and most beneficially, about 300 parts ofisopropenylvinylbenzene per million parts of the alkylstyrene. Thepresence of the isopropenylvinylbenzene in the alkylstyrene prior topolymerization enhances the gelling or thickening properties of theresultant polymer. Suitable polar compounds include acrylic acid,methacrylic acid, acrylamide, itaconic acid employed in a proportion offrom about 0.2 to 3 weight percent of the polymerizable componentscharged to the reactor. -If, with the alkylstyrene, less than 0.2percent is employed, suitable thickening is not obtained. If the levelof the polar compound is above about 3 percent, thickening is alsoimpaired. The most beneficial range for the polar compound is from about0.5 to 1.5 weight percent. Such polymers beneficially are prepared byemulsion polymerization employing conventional emulsion polymerizationprocedures. However, it is critical that in the preparation of suchpolymers no surface active agent, catalyst or other additive be employedwhich introduces a metallic ion into the system. Therefore, it ispreferred to 1 employ ammonium or amine salts of sulfonated fattyalcohols, alkylaryl sulfonates, long chain fatty acids such as lauricacid, palmitic acid, stearic acid and the like.

It is critical in the preparation of thickened fuels in 'accordance withthe present invention that the inclusion of non-volatile components berigorously avoided. By non-volatile components are meant componentswhich boil as components, or thermal decomposition products which onoxidation boil above about 400 C. For instance, it is essential andcritical that the inclusion of functional quantities of materialscontaining sodium, calcium, iron and like metallic elements, which onoxidation tend to form solid deposits, be rigorously avoided. Thegelation or thickening characteristics of the polymer are enhanced bythe addition of ionic material, but the cation and the anion of theionic material should volatilize when the fuel is oxidized.Consequently, base materials such as ammonium hydroxide and organic basematerials such as tetramethylammonium hydroxide or other organic basessuch as amines containing up to about 10 carbon atoms, includingprimary, secondary and tertiary amines, and quaternary ammonium saltssuch as methyl amine, ethyl amine, butyl amine, dimethyl amine, ethyleneamine, noctyl amine, aniline, N-methyl aniline, guanidine, are found tobe eminently satisfactory. Addition of the base materials to polymerscontaining acidic or hydroxyl groups generally prevents or markedlyreduces variation of viscosity with time. When it is desired to adddeicer compositions, such as ethylene glycol, the addition of a basematerial will provide maximum thickening characteristics. Usually, thebase is added to provide a concentration of from 2.5 X 10* to 0.5 molarsolution of the base in the thickened hydrocarbon. Generally, optimumthickening is obtained when the base concentration is from about 10* to10 molar when employing aqueous ammonia.

While obtaining gelation or thickening by the inclusion of suchmaterials as sodium hydroxide, sodium lauryl sulphonate and the likeprovides compositions of acceptable rheological characteristics, suchfuels tend to form deposits within an internal combustion turbine engme,such as a jet engine, and after a relatively short period of time, theengine becomes unsatisfactory because of sulfidation, more commonlyreferred to as Black Plague, and requires servicing. Minute amounts ofwater added to a thickened composition of hydrocarbon and polymerprovide enhanced thickening. However, such enhancement disappears aftera period of time, most frequently in about 24 hours.

The catalysts employed in the polymerization reaction advantageously arematerials such as ammonium persulfate and the like which result involatile oxidation products when oxidized in the presence of a liquidhydrocarbon. Similarly, the catalysts used in such a polymerizationbeneficially are ammonium persulfates and perborates, hydrogen peroxide,organic peroxides and hydroperoxides such as benzoyl peroxide,t-butylhydroperoxide, t-butylperbenzoateand the like. Azo catalysts arealso suitable such as azoblsrsobutyronitrile. Catalysts are generallyemployed at a level from about 0.05 to about 1 percent based on theweight of the monomer, and beneficially from about 0.1 to 0.5 percent.Emulsion polymerization is conveniently carried out by heating asuitable admixture of monomer catalyst and water to a desirablepolymerization temperature, beneficially from about 40 to C. The solidslevel for the latex advantageously is maintained at from 30 to 50percent, and beneficially about 40 weight percent. Advantageously, thepolymerization is carried out in a medium at a pH between about 3 and 6.Generally, it is advantageous to adjust the pH with a volatile alkalisuch as ammonia, either aqueous or anhydrous, to a value of about 4.2.Alternately, quaternary ammonium salts such as tetramethylammoniumhydroxide are employed with benefit, or ammonium salts such as ammoniumcarbonate, amonium bicarbonate are also satisfactory.

The polymers of the present invention are highly effective thickenersfor the previously specified aliphatic hydrocarbons. Such aliphatichydrocarbon and thickener combinations can be employed to greatadvantage in compositions where viscosity control or gelation isdesired. A particular application in which the present composition canbe employed with great advantage is in the manufacture of greases, whichapplication, depending upon the purpose for which the greases areformulated, presents a wide variety of thickening requirements. Anotherapplication is in the gelling of liquid rocket fuels to provide some ofthe advantages inherent only in solid rocket fuels.

The polymers of the present invention are employed with particularbenefit in the thickening of liquid hydrocarbon fuels. Mobile volatilehydrocarbon fuels such as jet or turbine fuel, diesel fuel, gasoline andother 'iike' hydrocarbon fuels may be converted into viscous liquids bythe incorporation of from about 0.2 to to 3 to 5 weight percent of thepolymers in accordance with the present invention. Beneficially, it isoften desirable to employ 0.5 to 3 weight percent, and advantageouslyfrom about 0.75 to 2.5 weight percent, of the polymers in accordancewith the present invention. Increasing the viscosity of such fuelscontributes significantly to their resistance to ignition in a crash orcollision wherein the fuel tank is ruptured. The precise mechanism ofsuch a flammability reduction is not fully understoodwhether this occursbecause of the high viscosity of the liquid and its resistance toforming small droplets, or whether this is a reduction in the vaporpressure of the liquid fuel, a reduction in the rate of vaporization, ora combination of all factors, or a combination of all factors and otherunknown factors. The flash point of the fuel composition appears to beraised when the thickening agents of the present invention are employed.The thickened fuels in accordance with the present invention are liquidswhich can be pumped and transported in conventional fuel storage andsupply means of vehicles or fixed storage. The more highly thickenedfuels of the present invention are fuels which are thixotropic clear toslightly cloudy liquids which, when subjected to shear, exhibit almostinstantaneous reduction in viscosity, and on removal of shearing forceexhibit an almost instantaneous recovery of the apparent viscositymeasured. The more highly thickened fuels of the present invention areapparently gels often times of a strinby and coherent nature. If thethickened solutions exhibit any true gel structure, they have a yieldpoint which is too weak to resist the force of gravity for extendedperiods of time. A more highly thickened solution in accordance with thepresent invention when disturbed, such as by being shaken in a closedcontainer, exhibits a lumpy surface, portions of the fuel clinging in asomewhat irregular manner to the sides of the container. The solutionalso exhibits characteristics such as stringiness or fibrousness whichcan be attributed to a gel. However, on standing for a relatively shortperiod of time, the solution has the general appearance of a liquid.Repeated inversion of a container having such a solution therein toentrap air bubbles in the solution gives the impression that thematerial is a gel; the bubbles slowly rise to the surface and thecontents of the container resume their liquid-like appearance. Rapidrotation of the container through about a one quarter turn and a rapidstop indicates that the material is viscoelastic in nature. Generallycircular oscillation of the 'fiuid occurs after the container has beenbrought to rest. A bubble rising through the thickened materialoftentimes will proceed at an irregular rate which suggests coherentregions within the solution. Portions of the liquid removed from thecontainer and placed on a flat surface appear to be a gel; however, onstanding form a puddle of liquid within relatively few minutes. Suchphenomena is concentrationand time-dependent; as the concentrationdecreases, that is, approaches 1 percent, the gel-like characteristicstend to disappear; whereas, when the concentration of the polymers isincreased in the hydrocarbon, such characteristics become more obvious.Viscosity of such solutions as measured by a Brookfield Viscometerprovides a linear plot when viscosity is plotted against the log of theshear rate indicating that the solution is a liquid and not a gel. Lesshighly thickened liquids in accordance with the present invention rangefrom viscous to liquid when concentrations of polymer are usedapproaching the minimum values and have the general appearance andcharacteristics of a true gel. As the concentration of the thickeningagent is increased, there is a gradual transition from what appears tobe a pure liquid to a more highly thickened solution with thehereinbefore described properties.

Of particular advantage are thickened liquid combustible fuels whichcomprise a major portion of an oxidizable liquid hydrocarbon havinguniformly dispersed therethrough a polymeric thickening agent, thecomposition being within the viscosity set forth in Table I below whenmeasured by a Brookfield viscometer Model RVI at 73 F. 11.5 F.

TABLE I Number 4 Spindle Number 6 Spindle Maximum Minimum MaximumMinimum viscosity, viscosity, viscosity, viscosity, Rpm centipoisecentipoise Rpm. centipoise centipoise Especially advantageous forgeneral service in internal combustion engines, particularly turbo jetengines, are compositions having an apparent viscosity of from about7500 to about 20,000 centipoise as measured at 10 revolutions per minutewith a number 6 spindle with a Brookfield Viscometer Model RVT at 73 F.:1.5 F. The composition is capable of flow under the force of gravityand is substantially free of ionic materials which result in nongaseouscombustion products when the composition is oxidized in air.Advantageously, the fuel composition contains from 0.5 to 5 weightpercent of the polymeric thickening agent, and beneficially from 0.75weight percent to about 2.5 weight percent.

Thickened hydrocarbons in accordance with the present invention arereadily prepared by dispersing polymers of the present invention withinthe hydrocarbon. Generally it is desirable to disperse the polymerwithin the liquid hydrocarbon employing high shear agitation such as isobtained in a colloid mill or a high shear agitator such as acentrifugal pump, gear pump, propeller-type mixer, serrated edge discmixer and the like. If desired, solution or dispersion may be hastenedby heating. Under agitation, the dispersion or solution appears liquid.However, when agitation is discontinued, the gel-like characteristicsbecome apparent. Therefore, for many applications, it is desired tosupply the thickening polymer in the form of fine particles oragglomerations of fine particles such as are obtained by spray drying ordrying a latex or aqueous suspension of the polymer at a temperaturebelow the film forming temperature of the polymer in a tray dryer, drumdryer and the like.

If a small amount of water is permissible in a particular applicationfor a thickened hydrocarbon, a latex of the polymer may be directlyincorparted into the hydrocarbon by agitation. The thickening effectdoes not appear to be significantly impaired. Generally whenincorporating a latex of a thickening polymer into a hydrocarbon, highspeed vigorous agitation is employed with benefit. The water-containingmixture usually has a distinct cloudy appearance rather than the clearto slightly cloudy appearance of solutions or dispersions prepared witha dry thickening polymer. If desired, the de-watering of the thickenedmaterial is accomplished by subjecting the dispersion of latex andhydrocarbon to a reduced pressure and fractionally distilling water fromthe system. Generally it is undesirable to raise the temperature aboveabout 80 C., as the thickening effect is reduced which may be due to thedehydration of the system and removal of trace amounts of water normallyfound in hydrocarbons of commercial purity.

Usually, optimum thickening is obtained by preparing a concentrateddispersion of the polymer in hydrocarbon and subsequently diluting tothe desired solids concentration with additional hydrocarbon material.Addition of alcohols such as methanol, butanol, ethylene-glycol and likehydroxylated compounds reduces the apparent viscosity of the thickenedhydrocarbons and alters the flow characteristics thereof. Usually suchan addition of alchols to a gel-like thickened hydrocarbon results inNewtonian or more Newtonian flow.

The following examples illustrate the manner in which the principles ofthe invention are applied but are not to be construed as limiting thescope of the invention. Unless otherwise noted, viscosities are measuredwith a Brookfield Model RVT Viscometer 24 hours after solution iscomplete at a temperature of 73 F.:l.5 F.

EXAMPLE 1 An agitated and jacketed reactor is charged with 82 parts byWeight of deionized water, 0.0264 part by weight ofethylenediaminetetraacetic acid. The reactor is closed, gases evacuateduntil an absolute pressure of about 127 milliliters of mercury isobtained. While maintaining agitation, the pressure on the reactor isreturned to atmospheric by adding nitrogen. This procedure is repeatedto remove air from the reactor. 0.164 part by weight of 28 percentaqueous ammonium hydroxide is added to the reactor and nitrogen addeduntil the pressure within the reactor reaches about 5 pounds per squareinch gauge. The contents of the reactor are heated to 98 C. and 56 partsby weight of a monomer mixture are added. The monomer mixture isprepared by mixing 65.4 parts by weight t-butylstyrene with 0.1 part byWeight methacrylic acid. A catalyst mixture is prepared by dissolving0.354 part by weight ammonium persulfate and 6 parts water. Two parts byweight of the catalyst mixture are added to the reaction mixture. Thereaction mixture is maintained at 98 C. by steam and water applied tothe jacket of the vessel. An exothermic reaction is indicated by a dropin temperature of the water in the jacket. After a period of aboutminutes when the temperature of the water in the jacket has risen to 98C., 0.5 part by weight of the ammonium persulfate solution is added tothe reaction mixture and the reaction continued until the jacket coolingwater and reaction mixture are both indicating 98 C. The reactor isvented to the atmosphere. The reaction mixture is a latex having asolids content of about 40 weight percent and a particle size of about2600 angstroms. The reaction mixture is cooled to about 30 C., filteredto remove coagulum and the resultant polymer recovered by tray-drying ata temperature of C. The tray-dried material is a fragile cake which isreadily crushed to a fine powder. Portions of the polymer are dissolvedwith vigorous agitation in a hydrocarbon mixture commercially availableas a jet aircraft engine fuel under the designation of Jet-A. A 2 Weightpercent solution of the polymer in Jet-A jet or turbine fuel gives aviscous stringy gel-like solution having a viscoelastic appearance whichhas a viscosity as measured on a Brookfield Viscometer employing o No. 6spindle at 10 revolutions per minute, of 15,000 to 25,000 centipoises;employing a 3 weight percent solution of the polymer in JetA jet fuel,the solution has a viscosity of 40,000 to 50,000 centipoise. Theviscosity ranges indicate the ranges obtained by employing variousbatches of JetA jet fuel.

8 EXAMPLE 2 The polymerization procedure of Example 1 is repeated withthe exception that 2 parts of the catalyst solution are added to thereactor immediately prior to the addition of 56 parts of monomermixture. Polymer is recovered by tray-drying and evaluated forthickening characteristics by dissolving the polymer in various samplesof JetA jet fuel. Viscosities of 15,000 to 20,000 centipoise areobtained measured in accordance with the procedure of Example 1 using aNo. 6, spindle at 10 revolutions per minute.

EXAMPLE 3 The jacketed agitated reactor is charged with 856 parts byweight of deionized water. The reactor is closed, evacuated to apressure of about milliliters of mercury absolute, filled with nitrogenuntil atmospheric pressure is obtained and the purging procedure withnitrogen repeated twice more. The water in the reactor is heated to 98C. with agitation and 1.2 parts by Weight of ammonium persulfate, 1.8parts by weight of 28 percent aqueous ammonia are added. The monomer isimmediately charged to the vessel. The monomer charge is a mixture of596 parts by weight tertiary-butylstyrene and 0.67 part by weightmethacrylic acid. The reactor contents are maintained at 98 C. for aperiod of 15 minutes after the jacket temperature rises to 98 C. Thereaction mixture is cooled and vented to the atmosphere. The reactionmixture is in the form of a latex having a particle size of about 1400angstroms. The conversion of monomer to polymer is 95 percent. Thepolymer is recovered by traydrying. A 3 weight percent solution of theresultant polymer is prepared employing JetA jet fuel as a solvent. Thesolution forms a stringy gel-like liquid having a viscosity of about31,000 centipoise using a No. 6 spindle at 10 revolutions per minute.

EXAMPLE 4 TABLE If Revolu- Lions per minute Concentration Percent:

TABLE II-Contlnued The procedure of Example 3 is repeated with theexception that the monomer mixture is pumped into the reactor over aperiodof about 12 minutes. The resultant latex particle size is inexcess of 3000 angstroms. Evaluation of the tray-dried polymer at 3weight percent solution in Jet-A jet fuel gives a gel-like solution witha viscosity of 28,000 centipoise at revolution per minute using a No. 6spindle.

EXAMPLE 6 An agitated jacketed vessel is charged with 1800 parts byweight deionized water. A sparger tube is positioned at the bottom ofthe vessel and the vessel sparged for 10 minutes with nitrogen. Thevessel is closed, heated to 80 C. 3.6 parts by weight ammoniumpersulfate are added. A monomer mixture of 10.8 parts by weight acrylicacid and 1789 parts by Weight t-butylstyrene are pumped at a constantrate into the vessel for a period of about 1% hours. The reactionmixture is maintained at a temperature of about 80 C. with agitation fora further period of about 1% hours. The conversion of monomer to polymeris 95 percent. The particle size of the latex is 7000 angstroms. Thepolymer is recovered by spray drying and 3 weight percent solution in Je't-A jet fuel gives a gel-like solution having a viscosity of 18,000centipoise using a No. 6 spindle at 10 revolutions per minute.

EXAMPLE 7 Employing the reactor of Example 6, 400 parts by weight ofdeionized Water are placed in the reaction vessel with agitation andheated to 98 C. and sparged with nitrogen. Two solutions are prepared:(1) a water solution of 450 parts by weight water, 0.6 part by weightammonium persulfate and 1.8 parts by weight of a 28 weight percentaqueous solution of ammonia; (2) a monomer solution which consists of 3parts by weight methacrylic acid 597 parts by weight l-butylstyrene. Thetwo solutions are simultaneously added to the vessel over a period ofabout 3 hours and the reaction mixture maintained at 98 C. for a periodof about minutes after addition of both streams is complete. A latex isobtained which is about 41 percent solids representing a monomer topolymer conversion of 95 percent. The polymer is recovered by traydrying and evaluated for thickening characteristics by preparing a 3weight percent solution in Jet-A jet fuel. The solution has a viscosityof 16,000 centipoise using a No. 6 spindle at 10 revolutions per minute.

EXAMPLE 8 A heated agitated vessel is charged with 856 parts by weightwater, purged with nitrogen while heating to 95 C. When the purge iscomplete, the following materials are charged as rapidly as possible:0.6 parts by weight ammonium persulfate, 1.8 parts by weight of 28percent aqueous ammonia solution and a monomer mixture of 600 parts byweight t-butylstyrene containing 600 parts per million oft-butylcatechol and 4 parts by weight methacrylic acid. The temperatureis controlled at 90 C. and after a period of 2 hours, the reactionmixture is cooled, filtered and spray dried to recover a polymer of linewhite powder. The conversion of monomer to polymer is 95 percent. Theparticle size of the latex in the reaction vessel is 1400 angstroms. A 2weight percent solution in Jet-A jet fuel is prepared. On standing,

10 the solution appears to form a gel-like liquid which has a viscosityof 11,000 centipoise using a No. 6 spindle at 10 revolutions per minute.

EXAMPLE 9 The procedure of Example 6 is repeated with the exception that10.8 parts by weight of acrylamide are employed instead of acrylic acid.The viscosity of a 3 weight percent solution is 6000 centipoise using a.No. 6 spindle at 10 revolutions per minute.

EXAMPLE 10 The procedure of Example 6 is repeated with the exceptionthat the monomer mixture is a 1:1 mixture of 2-ethylhexyl acrylate andt-butylstyrene. When 3 weight percent polymer is dissolved in Jet-A jetfuel, theviscosity of the solution is 4000 centipoise using a No. 6spindle at 10 revolutions per minute.

EXAMPLE 1 1 In order to illustrate the elfect of various non-metalliccations on the thickening characteristics of polymers prepared inaccordance with the invention, a plurality of solutions are preparedwherein a thickening additive is employed. The solutions are prepared byadding the thickener to the fuel with agitation. Where a deicer additiveis employed, the additive is mixed with a predetermined quantity ofthickened Jet-A jet fuel. The solutions are then permitted to stand for24 hours and the viscosity measured employing a Brookfield ViscometerModel LVF at 6 revolutions per minute and spindle as indicated in TableIII. The asterisks appearing after the numbers in the column titledPolymer Sample indicate the example from which the polymer is selectedfor evaluation. The chemical composition of the additive is indicatedunder Type Additive. The column headed Additive Quantity indicates thepercentage of additive based on the quantity of thickening polymer, andthe column Percent Gellant Polymer indicates the weight percent ofpolymer in the Jet-A jet fuel.

TABLE III Spin- Percent dle Polymer gellant Type Additive Viscos- N um-Sample polymer additive quantity 1 ity, ops. her

Example 1:

1 1. 25 None Control 5, 000 3 1.0 Control l 2. 0 Control 18,000 3 2.0NH40H. 0.50 32,000 4 Example 2:

1. 25 None. Control 50 1 1.25 Water.. 1.8 50 l 13 1. 25 NH4OH. 0.5012,000 4 Example 1; 14. 1.25 Anhy. NII 0, 00 3 Example 2:

15 1.5 Cont] ol 2, 000 -l-.

1. 25 TMAH l. 5t) 10, 000 4 1. 25 NaOH 2. 7 00 1 1.25 NaOH 0. 0 10,0004 1. 25 A1(OH):. 2. 7 2,000 3 1 Percent by weight, based on polymergallant.

2 Tetramethylammonium hydroxide (used as a. 00% solution of thopentahydrate).

3 Tetraniethylannuonium hydroxide pentaliydratv (solid).

4 Sparged.

In the preceding examples, the jet fuels contain no deicer additives.When the polymers alone are added to jet fuels containing deiceradditives, initial thickening will occur, but the viscosity rapidlydecreases in value. After one hour, a 2 percent solution of the polymerof Example 1 has a viscosity of 800 centipoise, and after 2 days, aviscosity of 300 centipoise. A 2 weight percent solution of the polymerof Example 1 is prepared in Jet-B jet fuel (which contains a deiceradditive) plus 0.5 percent by weight, based on the polymer, of 28percent ammonium hydroxide. After 2 days, the viscosity of the solutionis 14,000 centipoise; after 7 days, the viscosity is 15,000 centipoise.Adding tetramethylammonium hydroxide pentahydrate, the viscosity after 7days is 16,000 centipoise. A 2 percent solution in Jet-B jet fuelwithout deicer has a viscosity of 12,000 centipoise. Similar results areobtained when diesel fuel and gasoline with and without deicer additivesare employed.

EXAMPLE 12 A latex is prepared in accordance with Example 2 and dividedinto a plurality of samples. Table IV indicates the type of materialadded to the latex, the amount and the weight percent of resin in Jet-1Ajet fuel and the viscosity of the resultant solutions. The variouslatexes are dried in an oven at a temperature of about 60 C. for aperiod of 18 hours, the remaining dried polymer ground in a mortar andadded to Jet-A jet fuel.

TABLE IV Percent active Percent Visformpolymer cosity, Formulant ulant 1in fuel cps.

None Control 1. 25 60 0. 1. 32 100 0. 14 1. 100 NHOH 0.28 1. 25 400 0.56 1. 25 300 TMAH 3 0. l0 1. 25 2, 000 0. 1. 2, 000 TMAH 0. 1. 25 7, 0000. 60 1. 25 7, 000

1 Based on polymer. 2 Number 6 spindle at 10 revolutions per minute. 3Tetramethylammonium hydroxide.

EXAMPLE l3 Polymer prepared in the foregoing example has a solubilityparameter of about 8.45. Portions of the polymer prepared in accordancewith Example 1 are employed to make 3 weight percent solutions employinga variety of solvents. The results are set forth in Table V.

TABLE V Vis- Solvent an 1 cosity 2 Description Trimethyl pentane. 4, 000Apple sauce gel.

n-Pentane. Solid gel.

n-Heptane. Do.

n-Octane- Do.

Isooctane Do.

Necane Do.

Cyclohexane Solid gel-slightly viscoelastic.

Toluene 8. 93 35, 000 Viscoelastic.

Benzene 9. 16 35, 000 Do.

o-Dichlorobenzene 10. 0 70, 000 Do.

N itromethane 12. 7 Polymer doesn't disperse.

l Solubility parameter.

?Brt0okfield viscometer Model LVF #4 spindle at 6 revolutions per mmu e.

3 Having the appearance of apple sauce as commercially available.

4 No thickening.

EXAMPLE 14 12 tained at this temperature. for 4 hours. The reactionproduct is recovered by tray drying in the form of a fine white powder.A 3 weight percent solution of the polymer obtained by tray drying isformed in Jet-A jet fuel. The solution has a viscosity of 5000centipoise as measured at 10 revolutions per minute with a No. 4spindle.

EXAMPLE 15 A flammability evaluation apparatus is employed. Theapparatus comprises a gun, the barrel of which is 40 feet in length and8 inches in diameter. The sample to be evaluated is placed in a cylinderof foamed polystyrene having one inch thick walls. The fuel to beevaluated in turn is placed in a double-walled polyethylene bag andplaced in the foam cylinder. The fuel to be evaluated in the foamcylinder are placed in the breech of the gun. The gun is pointed in ahorizontal direction at a vertically disposed steel grating positionedabout 20 feet from the muzzle of the gun. Remote from the gun andadjacent to the grating are five pans about one foot in width, 2 feet inlength and 4 inches deep filled with Jet-B jet fuel. The pans arearranged in a rectangle with one pan centrally disposed; one edge of therectangle is parallel to the grating. The rectangle is about 10 feet ona side. The closest pan is about 10 feet from the grating. The Jet-B jetfuel is ignited. The foam container is then fired into the grating at amuzzle velocity of about 90 miles per hour and the ignitioncharacteristic of the resultant fuel spray is visually observed andrated in the following mannet:

(1) 100 percent reduction of explosion-no flaming;

(2) to percent reduction of explosion-very slight flaming;

(3) 50 to 60 percent reduction of explosion-slight flam- (4) ZO to 30percent reduction of explosionthere is a definite explosion with a smallfire ball;

(5) 0 to 20 Percent reduction of explosionthere is a large explosion andfire ball.

Jet-A jet fuel and Jet-B jet fuel with polymer as prepared in Example 1are evaluated and the results are set forth in Table VI.

lEXAMPLE 16 The procedure of Example 15 is repeated employing polymerprepared in accordance with Example 4 wherein a 2 percent solution ofthe polymer is prepared in Jet-A jet fuel and portions of this solutiondiluted to obtain concentrations of 1, 1.25 and 1.5 percent. The resultsare set forth in Table VII.

TABLE VII Brookfield viscosity at Explosion 10 rpm. cps. rating Polymerconcentration Jet-A jet fuel, weight percent 1 Prepared by dilution of2% solution with fuel.

13 EXAMPLE 17 A sample of JetA jet fuel is thickened with 2 weightpercent of the polymer of Example 1 and is pumped to a I-47 jet(turbine) engine. The engine operates satisfactorily on a stationarytest stand on the thickened fuel and no malfunction or sulfidation isobserved.

EXAMPLE 18 A portion of the polymer of Example 1 is dissolved at variousconcentrations in JetA jet fuel and 24 hours after solution is completethe viscosity of the solutions is measured at varying shear rates atabout 25 C. with a No. 6 spindle. The results are set forth in TableVIII.

TABLE VIII Revolu- Viscostions ity in per centi- Concentration minutepolses Percent:

EXAMPLE 1 9 A plurality of 150 gram samples of a solution of 1.25 weightpercent of the polymer of Example 1 is treated with varying quantitiesof aqueous ammonium hydroxide and a viscosity response which occurs ismeasured. No significant alteration in viscosity is observed from about2 microliters per 150 grams to about 200 microliters at 10 revolutionsper minute with a No. 6 spindle. About 2.5 microliters of 28 percentaqueous ammonium appears to be optimum, and quantities from 0.2microliters and higher appear eminently satisfactory. The increase inviscosity is most noted at low shear rates; that is, shear ratescorresponding to 5 revolutions per minute and less where maximumviscosities are observed at a concentration of about 3 microliters per150 grams of 1.5 weight percent of polymer dissolved in Jet-A jet fuel.

Similar results are obtained when the procedures of the foregoingexamples are repeated employing p-tertiaryamylstyrene, m-n-hexylstyrene,p-tertiary-hexylstyrene and mixtures thereof in place ofp-tertiary-butylstyrene.

As is apparent from the foregoing specification, the present inventionis susceptible of being embodied with various alterations andmodifications which may differ particularly from those that have been inthe preceding specification and description. For this reason, it is tobe fully understood that all of the foregoing is intended to be merelyillustrative and is not to be construed or in- 14 terpreted as beingrestrictive or otherwise limiting of the present invention.

What is claimed is:

1. A thickened hydrocarbon comprising a hydrocarbon body containinguniformly incorporated therein from about 0.2 to about 10 weight percentof a synthetic organic alkyl styrene or lauryl acrylate latex polymersoluble in the hydrocarbon body, the polymer having at least 0.2 to 3weight percent, based on the weight of the polymer, of anoxygen-containing polar compound selected from the group consisting ofolefinically unsaturated copolymerizable (a) acids containing up to 6carbon atoms, and (1b) amides containing up to 4 carbon atoms such asacrylamide, and mixtures thereof; -(c) hydroxy acrylic esters such as2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate,3-hydroxypropyl methacrylate, 2- hydroxyethyl acrylate, 2-hydroxypropylacrylate, 3-hydroxypropyl acrylate; (d) sulphonic acids such as 2-sulphoethyl methacrylate, 2-sulphoethyl acrylate,3-vinylbenzenesulphonic acid, 2-benzenesulphonic acid and the like.

2. The composition of claim 1 wherein the polymer is a polymer of analkylstyrene.

3. The composition of claim 1 including a metal-free base wherein thebase is ammonia.

4. The composition of claim 1 wherein the polymer is present in aproportion of from about 1 to about 4 weight percent of the composition.

5. The composition of claim 4 wherein the polymer is present in aproportion of from about 1.25 weight percent to about 2.5 weightpercent.

6. The composition of claim 1 wherein the polymer is a polymer oft-butylstyrene.

7. The composition of claim 6 wherein the polymer is a polymer oft-butylstyrene and methacrylic acid.

8. A hydrocarbon fuel composition suitable for internal combustionengines such as turbo jet engines, the fuel composition being a pumpableliquid having the appearance of a viscoelastic fuel, the fuelcomposition comprising a major portion of liquid combustiblehydrocarbons and from 0.2 to 5 weight percent of a polymeric thickeningagent, the polymeric thickening agent being an alkyl styrene or laurylacrylate latex polymer containing from about 0.5 to about 3 weightpercent, based on the weight of the polymeric thickening agent, of anoxygen-containing polar compound polymerized therein, the polar compoundbeing an acid containing up to 6 carbon atoms or an amide containing upto 4 carbon atoms, the composition being substantially free of materialswhich induce sulfidation in a turbo jet internal combustion engine.

9. The composition of claim 8 wherein the hydrocarbon fuel is jet fuel.

10. The composition of claim 9 wherein the polymeric thickening agent isa polymer of an alkylstyrene and a carboxylic acid.

11. The composition of claim 10 wherein the polymeric thickening agentis a polymer of t-butylstyrene and methacrylic acid.

12. The composition of claim 10 wherein the polymeric thickening agentis a polymer of t-butylstyrene and acrylic acid.

13. The composition of claim 8 including a volatile base.

14. The composition of claim 13 wherein the volatile base is ammonia.

15. A method for the preparation of a thickened hydrocarbon, the stepsof the method comprising:

providing a liquid combustible hydrocarbon fuel,

providing a synthetic organic polymeric thickening agent, the polymericthickening agent being an alkyl styrene or lauryl acrylate latex polymerhaving polymerized therein from about 0.5 to about 3 weight percent,based on the weight of the polymer, of an oxygen-containing polarcompound, the polar com- 15 pound being an unsaturated copolymerizableacid or amide containing up to 5 carbon atoms, admixing the polymericthickening agent and the liquid fuel until the thickening agent isgenerally uniformly incorporated throughout the combustible hydrocarbon,discontinuing mixing, thereby providing a pumpable viscous fuelcomposition having the appearance of a viscoelastic gel. 16. The methodof claim 15 including the step of incorporating a minor amount of a basetherein.

17. The method of claim 16 wherein the base, polymer and liquidhydrocarbon are simultaneously admixed.

16 References Cited UNITED STATES PATENTS 2,504,779 4/1950 Young et a1.447 D 3,219,619 11/1965 Dickerson 447 C 3,391,081 7/1968 Conrady 44-7 CBENJAMIN R. PADGETI, Primary Examiner U.S. Cl. X.R.

